How Your Gut Bacteria May Be Controlling Your Brain

Tasha Levytska /
Tasha Levytska / | © Culture Trip
Tor Cardona

Wellness editor

The gut has made a sudden rise to prominence as an arbiter of overall health. It’s well established that gut bacteria, also known as the microbiome, can influence digestion, allergies and metabolism. But these microbes’ reach may extend much further – into the brain. Conditions including depression and anxiety are now being linked to the digestive system.

The brain may be one of the most complex objects known to humankind, but science has suggested the digestive system is of equal importance, especially when it comes to our emotional health. Your gut is teeming with trillions of bacteria, making up what’s known as the microbiome. Collectively weighing up to two kilograms (heavier than the average brain), the microbiome plays a vital role in your health, breaking down food, supporting immunity and, perhaps surprisingly, affecting mood. Nutritionist Rebecca Pilkington believes keeping the microbiome balanced is the key to optimal physical and mental health. “If your gut is out of whack,” she says, “this can lead to inflammation, believed to be one of the biggest causes of depression.”

It all comes down to the gut-brain axis. “Your gut and brain are connected by the vagus nerve – one of the biggest nerves in the body that’s essentially an information superhighway,” Pilkington says. This two-way line of communication can trigger your gut to mirror your current state of mind – or vice versa – explaining why you may feel nauseous before a presentation or why stressful situations wreak havoc with your stomach.

The vagus nerve also plays a key role when it comes to stress and mood. In 1921, Otto Loewi, a German physiologist, discovered that electronically stimulating the vagus nerve caused a reduction in heart rate. Since then, researchers have confirmed the vagus nerve doesn’t respond well to emotional stress. The more anxious and stressed we are, the higher the likelihood of inflammation and low mood, potential triggers for depression.

Moreover, 95 percent of serotonin, the body’s happy hormone, is created in the gut, as well as mood-boosting dopamine, which is why the gut is increasingly referred to as the ‘second brain’. If gut bacteria falls out of sync, this can fuel the gut-brain feedback loop, negatively affecting mood. Hormonal changes triggered by the body’s stress response can also take their toll on the gut. Many sufferers of irritable bowel syndrome (IBS) claim anxiety and stress are their main triggers.

Nutritional therapist and gut expert Eve Kalinik believes that when we are anxious, we shift into a ‘fight or flight’ mode which can affect the digestive system, causing it to ‘hold’ or ‘release’, i.e. causing either constipation or diarrhoea. This may be the explanation behind stress-related tummy troubles.

Kelly Brogan MD, a New York-based holistic women’s health psychiatrist and author of A Mind of Your Own, also believes gut inflammation is the root cause of depression. “Not one valid study has proven that depression is caused by a chemical imbalance in the brain,” she says. Her belief is that the most effective way to treat mental health disorders is through the gut. It may sound controversial, but recent studies have suggested depression could be treated using anti-inflammatory drugs.

The symbiotic relationship between the gut and mental health means the happier your bacteria are, the happier you’ll feel. One of the simplest ways to keep the digestive and nervous systems in harmony is to reduce stress levels, says Natalie Lamb, a nutritional therapist at Bio-Kult. “Deep breathing can help keep your vagus nerve strong and healthy,” she says. “Practice this regularly and also consider yoga and meditation. Also be mindful of staying active but be wary of overdoing it, which can raise cortisol levels and drain energy, negatively affecting the gut-brain connection.”

To help restore balance to the microbiome – which can be affected by antibiotics and processed foods – Lamb advises a Mediterranean-style diet. Aim to consume plenty of good-quality protein, which is high in amino acids – the building blocks for brain neurotransmitters such as serotonin – and oily fish as well as antioxidant-rich seasonal fruits and green vegetables, which are rich in magnesium, a mineral that plays a central role in the nervous system.

And when it comes to probiotics – deemed the holy grail of gut health – Pilkington says they are worth considering if you suffer from brain fog or even anxiety and depression. “Eating probiotic-rich foods, such as kimchi and sauerkraut, or taking a high-quality supplement, can help.”

While there’s still much to uncover about the mystery of the gut, experts are adamant that the balance of the microbiome is hugely important in both digestive and brain health. “What is happening in the gut has a huge impact on mental health,” says Pilkington. Perhaps when it comes to mental health, you really are what you eat after all.

Wednesday 10 October is World Mental Health Day. To highlight this, Culture Trip is looking at how different societies are shining a light on this important issue in innovative and alternative ways.

The content of this article is provided for general information only and is not an attempt to practise medicine or give specific medical advice, including, without limitation, advice concerning the topic of mental health. The information contained in this article is for the sole purpose of being informative and is not to be considered complete, and does not cover all issues related to mental health. Moreover, this information should not replace consultation with your doctor or other qualified mental health providers and/or specialists. If you believe you or another individual is suffering a mental health crisis or other medical emergency, please seek medical attention immediately.

If you are experiencing mental health issues, in the UK, Samaritans can be contacted on 116 123 or email You can contact the mental health charity Mind by calling 0300 123 3393 or visiting Please note there are no affiliations of any kind between the aforementioned organisations and Culture Trip.

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